In the past there have been available machines which, individually, performed certain functions needed in educational and/or psychological testing. There have been many devices to measure the minimum loudness which a human ear could detect and they have permitted the testing of the ears individually or together. There have been other devices which attempted to measure the auditory memory of humans being tested. These prior instruments have been separate from one another and each a complicated and expensive machine. Each test for loudness capable of being heard, of auditory memory, or auditory side-dominance, etc. needed a separate, expensive apparatus. In some cases the apparatus has been unreliable or at best required careful calibration.